This article investigates musical grit and sisu, inner fortitude, as predecessors of flow, flourishing and personal growth. Grit has been identified as an important factor for success. Our aim was to increase knowledge of the benefits of intensified music education for building grit, resilience and fortitude. Data were collected with mixed methods in 2020 from two schools and 96 children. Surveys were filled out by students in both music and regular classes. Qualitative data about music education experiences were collected through interviews and writing tasks from the music class students and interviews with their teachers. Music classes scored higher than regular classes in perseverance, certain dimensions of flow and musical flourishing. Musical flourishing correlated with playing years and had high correlation with self-efficacy, flow experiences and general well-being. The sequence of facing, but also beating, challenges as a group in musical performances and then feeling flow and flourishing seemed to be beneficial for children’s personal growth. Students in music classes learned not only musical skills, but also resilient and optimistic thinking related to their challenges. The theoretical model of Trust, Hope and Love was revised to display how sisu, the inner fortitude, advances flourishing.